Apparatus for reproducing sound on film



July 29, 1941. JJRABINOWITZ APPARATUS FOR REPRODUCING SOUND 0N FILM Filed June 16. 1958 2 Sheets-Sheet 1 INVENT'ORI July 29, 1941. J. RABINOWITZ APPARATUS FOR REPRODUCING SOUND ON FILM Filed June 16, 1938 2 Sheets-Sheet 2 14:05 PfiB/NUW/TZ Wows? Patented July 29, 1941 UNITED STATES PATENT OFFICE Jacob Rabinowitz, Brooklyn, N. Y.

Application June 16, 1938, Serial No. 214,016

4 Claims.

This invention relates to a new and unique method of reproducing sound on film, for use in combination with any home film projecting machine whereby my pre-stage amplifier and oscillator apparatus is adaptable for use through the medium of any type of a radio, without the use of an expensive amplifier or speaker.

A salient feature of my invention is that in the present production of silent home projectors and to those who are constructing sound attachments for use in silent picture machines, it will be possible to buy these attachments and with the use of my pre-stage amplifier and oscillator, a very inexpensive, but effective means in obtaining a greater fidelity of reproducing sound on film is possible through the use of ones own radio.

Another salient feature of my invention is that the operation of my pre-stage amplifier and osci1- lator in combination with the projector and radio is very simple, there being but one control to regulate the volume. This one control or potentiometer acts two-fold in one operation, such as, controlling the modulation into the oscillator and also in the audio frequency output.

Another salient feature of my invention is that although my invention proposes coupling the output of my pre-stage amplifier and oscillator to the lead in wire leading to the radio, (antenna or aerial), it is also possible, if it is not convenient to couple the output of my pre-stage amplifier 1 Another important feature of my invention is I that it embodies all the necessary elements to reproduce faithtfully through the radio including ground P. E. C. voltage and exciter voltage. Present methods now proposing sound head attachments for silent projectors now in use, need only supply the mechanical reproducer, and by a plug method with the use of my pre-stage amplifier and oscillator can connect the necessary operating voltage for P. E. C. and exciter.

Another important feature is that in the prior art of reproducing sound on film in order to deliver truly linear and distortionless audio power amplifiers must be built with precision equipment therefor, becoming prohibitive for the use of the average person or home. In my method it is quite apparent, by my accompanying description and illustration, that in as much as my pre-stage amplifier and oscillator does not embody expensive equipment for reproducing sound on film, the

radio frequency output of my pre-stage amplifier and oscillator is then dependent upon the I. F. and R. F. stages of the radio to further modulate the output of the amplifier and oscillator, then through the A. F. stages of radio which will reproduce true reproduction, in other words, the reproduction of the sounds on film through my invention will maintain quality and fidelity, with the same equality as a radio program is received.

Another important feature of my invention is that while my pre-stage amplifier-oscillator apparatus is shown as a separate unit or device, adjacent to the moving picture projector, it may be, if so preferred, embodied into one panel or assembly with the projector.

Other important features of my invention will appear, as the description proceeds, in the following specifications and the accompanying drawings, in which Figure 1 is a complete wiring diagram of my amplifier-oscillator apparatus.

Figure 2 is a separate wiring diagram of the tubes filaments connections in a D. C. circuit.

Figure 3 is a similar diagram showing the tubes filaments connections in an A. C. circuit.

Figure 4 is a plan view of my complete amplifier-oscillator apparatus.

Figure 5 is a front view of the same apparatus.

Figure 6 is a view similar to Figure 5, reduced in scale and showing an alternative form of assembling the tubes in a horizontal position.

Figure '7 is a perspective view illustrating the complete hook-up of my apparatus with the radio.

Figure 8 is a perspective plan of an alternative method of the use of a source of light projecting onto a mirror, which reflects to the photo electric cell.

Figure 8a. is an alternative wiring hook up, whereby an additional condenser and resistancechoke is placed next to the coupling condenser for a tone control.

Referring to the drawings in Figure 1 of my complete pre-stage amplifying and oscillating system, in which the exciter I actuated by a resistor 2, receives current from any D. C. or A. C. source of supply, (which may or may not have a transformer on A. C.). Exciter l sends a light beam through a slit or aperture, not shown, within the optical unit 3 whereby the light beam is reproduced through the slit or aperture 3a on the sound track of the film F, which may be of any desired width, preferably on 16 mm. films, thence the light beam reflects to the photo-electric cell P. E., the anode 4 of the P. E. cell being connected to a Wire 5 passing through a shielded cable 5 having a resistance 1 which is coupled to a mica condenser 8, also connecting to a resistance 9 grounded at 5, to which also the shielded cable ii is grounded through the wire li. Resistances and 53 are used to cut the current irom the high voltage line i i to the necessary operating voltage of the P. E. cell. The cathode id of the P. E. cell is also connected to ground ll such as for example, through the shielded cable which continues to an additional condenser 5*; encased in metal, thence to grid l"! of the amplifier tube 58, the suppressor element iii in the tube being connected to the cathode and resistance 2% to ground ill, and is also blocked by a l'urther condenser 22. Screen grid oi the amplifier tube i8 is connected through another resistance 24 to the high voltage line 25, and also has a iurt er resistance '25 connected to ground it and Cur. nectin also to a condenser The output oi the amplifier tube :8 is connected to a coupling condenser 29 which is also provided with a resistance 39 to the high voltage line 25. The condenser 29 continues through the line 29 to the grid of the power amplifier tube the condenser having also a resistance 33 to ground it. The element 34 is provided with filtering condenser 33a for reducing hum level and connects through a resistance to ground l9, element connects within the power amplifier 0U tube 32 to the element and to high voltage line to obtain screen grid voltage for the power amplifier tube The output 37 of the power amplifier tube is then coupled through the line 38 to the primary 3%) provided with a condenser of a suitable output transformer through line all connecting to the high voltage line 25 and is further connected through line M to the output of the power amplifier tube E2. The secondary 3,3 of the output transformer 55 is connected at to one end of the volume and modulation control 35, which may be known as a potentiometer and is connected at the other end to line it through lines 43 and 45 to the switch contact control 55, having condenser connecting at 52a to the line 33 and the switch 53 and ground connecting to the house line volt- 55. The line 38 continues into the coil 52 which has the proper inductance and when used in connection with the variable condenser 53 has a frequency range suitable to the broadcast band.

It is to be noted that the inductance coil 52 is tapped at a suitable point 55, connecting to lin 55, to which a resistance 55 connects to line 51 of the condenser 58 connects to the induction coil 52 and further through line 5! to the grid cap 59 of the oscillator tube Bil. The cathode Bl of the oscillator tube 60 is connected to line 55, and the arm 82 of the potentiometer 45 connects to the suppressor element 63 of the oscillator tube 60. The plate 64 in the tube Bl] is connected to a radio frequency choke 55 of any suitable design, and the other end of the choke 65 is connected to the screen grid 56 of the tube 66. The secondary 67 of the radio frequency choke 65 is wound suitably to obtain suificient radio frequency current output and is wound closely to the primary of the choke E5. The radio frequency choke 65, whose secondary is provided with two leads, GB and 69, either of which may be connected to any radios, lead in wire, loll or aerial.

The filtering choke i0 is used in conjunction with two suitable condensers, H and 12, on both sides of the choke ill for filtering the line cirrent to eliminate hum. Resistances i3 and 74 are used in the circuit to supply the proper 75 current to line '15 to the oscillator tube 60 and through the choke 55, which fixes the radio frequency output of the oscillator. The filtering choke 10 leads to the cathode 18 of the rectifier tube "H and it is to be noted that the oathodes 75 are connected in parallel, and both plates :8 in the rectifier tube Ti are also connected in parallel through line 19 to house line supply line til to contact switch 55, the other end 8| of the filtering choke 7U furnishes the filtered high voltage.

The filaments A, B, C and DD of the amplifier tube l8, power amplifier tube 32, oscillator tube 60 and the rectifier tube 17, respectively, are shown connected in series by a resistor inserted at a contact point 45a for reducing line voltage to the proper operating voltage for said tubes. The filament circuit either in A. C. or D. C. current, shown in Figures 2 and 3 may control any number of tubes, whether metal or glass, other than shown, by inserting a resistor similar to 90 of a clifierent value. The A. C. and D. C. circuit shown in Figure 2 comprises the resistor 99 from which line Bl leads to the filament A of th amplifier tube l8 which is connected line to and through the filament B of the power amplifier tube 32 through line 86 to the filament C of the oscillator tube 60, through line 9! to the double filament DD of rectifier tube i! and through line 98 to supply line current 89. The component parts 52, 56 and 58 are shielded with a metal shield, SI, and the amplifier tube 18 is also shielded by a metal shield, S2.

The chassis or box mounting C2, inclosing all the wiring connections, is grounded to point 4%, through line 49, and the amplifier oscillator output line 68 or 69, are optionally coupled at 89, to the radio antenna or lead in wire I00, to the radio R. The radio frequency current from the pro-stage amplifier oscillator, is induced in the lead in or antenna wire [00, by the coupling of line at 68 and 99, or this may as well apply to the line 69, either of which is optional.

In operation (see Figure 7) of my apparatus, the motion picture projector MP is connected up with the sound film F and my pre-stage amplifier and oscillator system, through the apparatus A0 is then turned on by the switch 50. Lead 68 is then coupled loosely to the antenna 99 connection to the coupling line 68 thereby connecting to the radio R which is then turned on and then tuned where no broadcast is heard. It is then noted on the radio what frequency it is tuned to, for example, the radio is tuned to 1100 kc. then my pro-stage amplifier-oscillator is set by the tuning adjustment of the variable condenser now 53a also to 1100 kc. so as to correspond to the frequency on the radio. At this point my pro-stage amplifier-oscillator and radio are now tuned to the same frequency. The switch SW of the motion picture projecting machine PM is turned on, then the picture is projected on the screen S, then modulation and volume control E2 is then tuned on to the desired volume needed for the reproduction of sound through the sound track ST of the film F as it runs in between photoelectric cell PE and the light beam from the optical unit 3.

In operating my apparatus the amplifier type of oscillator volume control may be set to a point where a given output R. F. C. (radio frequency current) and therein to be solely controlled by the volume control of the radio, this being done when the picture is running, and it is not necessary for one to be at my apparatus adjacent to the film projecting machine for volume adjustments, but may, however, be at the radio and control the volume adjustments at that point.

Practice generally at present is for one to go to the projector to adjust the volumecontrol. My apparatus is adaptable for use on A. C. or D. C. current, such as through the rectifier tube 11, and also eliminates Wire leads that are commonly used in connecting the output of the amplifier to the speaker; this must be drawn to the point where the picture is shown on the screen. In my pre-stage amplifier-oscillator apparatus, only a single wire, such as 68 or 69 in the wire diagram, is hooked on to the antenna or aerial of the radio, which are insulated, nevertheless, the Wire 68 or 69 is merely wrapped around the lead in wire, the antenna or aerial of the radio R, for its induction therewith, and the volume control is then controlled either at the radio or projector, whichever is more convenient. Some results have been obtained by my pre-stage amplifier-oscillator apparatus, without the connecting wires 68 and 69 coupled to the lead in wire or operative controls, the wiring therewith being arranged within the hollow portion of the chassis, as shown in the broken away section of Figure 5. In these Figures 4, 5, 6 and '7, my pre-stage amplifier oscillator apparatus is clearly illustrated and therefore no constructive description is deemed necessary.

The wire diagram, shown in Figure 1, is a complete disclosure of the operating functions of my method to reproduce sound on film through the medium of any type radio in combination with a sensitive photo electric cell for amplifying sound variations received therewith.

It is also to be noted that my apparatus approximately comprises 75% less parts, such as tubes, etc., that are now used in expensive amplifying sets and the extra speaker, and still my pre-stage amplifying and oscillating system maintains a greater quality and fidelity in sound reproduction as hereinbefore described.

It is to be further noted that I may, if so desired, arrange all the tubes I8, 32, B and H in a horizontal position, such as shown in Figure 6, thereby providing a more compact assembly and apparatus than as shown in the vertical position of Figures 4, and '7. electric cell PE in such a manner as shown in Figure 8 whereby a mirror M reflects the projected source of light B from the optical-lens unit 3 to the photo electric cell PE wherever space is limited which prevents positioning the PE cell in direct alignment with the light beam as shown in Figure 1.

It is to be noted that the type of current, whether A. C. or D, C., when used on a D, C., the rectifier 11 can be used as a voltage doubler or a half way rectifier. Also needs for a tone control is provided as shown in Figure 8a in which the coupling condenser 29 is connected to an additional condenser 29a and potentiometer resistance 2% connected at Zfic to line 29d to ground Iii. This Figure 8a is an alternative form of that portion of the wire diagram adjacent to the condenser 29.

It is also to be understood that my description of my pre-stage amplifying and oscillating sys- Also I may use my photo tem discloses one control supplying percentage of modulation to the oscillator and amount of audio frequency output; another volume control may be inserted in the grid current of tube 32 to control the audio frequency output, if so desired.

It is also to be understood that the inventive idea is capable of many other uses, not disclosed, but which will be apparent to those familiar with the art to which my invention relates. Furthermore, only those portions of the sound reproducing system considered necessary are shown for a complete understanding of my invention.

It is likewise to be understood that all similar parts reproduced in alternative form, upon the drawings, may be designated by priming accordingly, and also any part of my invention may be altered that may come within the spirit of my invention and the scope of the appended claims.

Having thus described my invention, what I claim is new, and desire to secure by Letters Patent, is as follows:

1. In a device for the reproduction of sound from an optical sound record by a radio receiver having an antenna circuit responsive to a modulated carrier wave, the combination with an exciter supplied with ordinary house current and a photo-electric cell for receiving light from the exciter modulated by the optical sound record, of an audio-frequency amplifier having its input connected to the photo-electric cell, an oscillator including a plate for supplying a high frequency carrier wave and including a grid for modulating said wave and a suppressor grid, a transformer having its primary connected to the output of the amplifier and its secondary connected to the first named grid of the oscillator to modulate the carrier wave, and a closely coupled radio choke having its primary connected to the plate of the oscillator and to the second named grid of the oscillator and the secondary of said choke inductively coupled to the antenna circuit of said radio receiver.

2. In a device for the reproduction of sound from an optical sound record by a radio receiver having an antenna circuit responsive to a modulated carrier wave, the combination with an ex citer supplied with ordinary house current and a photo-electric cell for receiving light from the exciter modulated by the optical sound record, of an audio-frequency amplifier having its input connected to the photo-electric cell, an oscillator including a plate for supplying a high frequency carrier wave and including a plate for supplying a high frequency carrier wave and a grid for modulating said wave, a transformer having its primary connected to the output of said amplifier and its secondary connected to said grid of the oscillator to control the modulation of said carrier wave, and means connected with said plate for introducing said modulated carrier wave into said antenna circuit of said radio receiver.

3. In a device for the reproduction of sound from an optical sound record by an apparatus such as a radio receiver having an antenna circuit responsive to a modulated carrier wave, the combination with an exciter supplied with ordinary house current and a photo-electric cell for receiving light from the exciter modulated by the optical sound record, of an audio-frequency amplifier having its input connected to the photoelectric cell, an oscillator for supplying a high frequency carrier wave, a transformer having its primary connected to the output of the amplifier, a resistor connected across the secondary of said nary house current and a photo-electric cell receiving light from the exciter as modulated by the sound record, of an audio-frequency amplifier connected with said photo-electric cell, a high frequency oscillator for generating the carrier Wave, and a transformer having its primary connected to the output of the amplifier and its secondary connected to the oscillator to modulate the carrier Wave,

JACOB RABINOWITZ. 

